The revelation prompted a furious reaction yesterday from Ukip leaders who called on him to resign his membership, but Mr Kilroy-Silk kept Ukip guessing by refusing to declare publicly what he would do now.

Speculation was growing last night that he could use a meeting in his East Midlands European constituency on Thursday to announce his resignation from the party.

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In an interview for BBC Radio 4's The World at One, he said: "All I can say is that I have been inundated for a long time, from people within Ukip and outside, from all parties and from none, saying that we need a new party."

Mr Kilroy-Silk aims to use Veritas to tap into what he believes in widespread public disillusionment with the existing main political parties. "There is clearly a huge demand across the country, across people's background in ages and indeed, across the old parties, for something that is fresh and new, and which will represent them and Britain's interests," said Mr Kilroy-Silk.

The former Labour MP believes Ukip in its present form is failing to respond to that public mood.

Though attention will now focus on his address to the meeting on Thursday, Petrina Holdsworth, the Ukip chairman, yesterday called on the MEP to declare his hand without delay.

"If he feels he must set this [party] up, so be it, but I would like him to resign immediately," she said. She blamed Mr Kilroy-Silk's expected next move on his failure to win the leadership of the party he only joined last Spring.

"Quite clearly, he was quite satisfied with Ukip in that he wanted to lead it, for goodness sake. So to start throwing mud at us now seems a little strange," said Mrs Holdsworth.

She cited to have a copy of a Veritas manifesto, ridiculing it as a "parody of Ukip".

She said that the manifesto contained proposals on immigration, which included refusing a visa to anyone who is seriously ill with tuberculosis or Aids and, on law and order, proposing that pubs selling drink to underage youngsters should be fined their entire day's takings.

But Mr Kilroy-Silk last night insisted the document was not genuine.

• A new campaign to ensure that the next House of Commons has a majority of Euro-sceptic MPs is unveiled today at Westminster.

The 330 Campaign, to be launched by Ukip member Paul Gilbert, will ask would-be MPs to give a public declaration that they would vote for all legislation that would facilitate Britain's withdrawal from the European Union.